This invention relates to orthopedic appliances for correcting Class II malocclusion in children and adults in which the upper row of teeth are found considerably ahead of the lower row. Class II malocclusion produces an abnormal bite and detracts from the individual's appearance. Orthodontists correct this situation by slowly moving teeth under pressure, accompanied at times by the extraction of certain teeth and in some cases retarding maxillary growth to bring the upper and lower rows of teeth into an alignment more suitable for efficient and comfortable mastication. This process of moving teeth - "orthodontics" may be accomplished by the use of a wire fastened to each tooth in either or both the upper and lower dental arches. These arrangements, called arch wires, exert forces on the teeth which gradually induce them to move into the desired position. Aside from orthodontics, one method of improving the mandible-maxilla relationship is to couple the upper and lower jaws with various types of linkages so that natural closing and opening movements of the patient during speaking and chewing, force the lower jaw (the mandible) into an improved position with respect to the upper jaw (the maxilla). The opening or closing forces of the jaw muscles are thus utilized to bring about the desired correction. Because a permanent change in the positional relationship of the jawbones, rather than the movement of individual teeth is accomplished, this practice is termed "dental orthopedics". Some appliances for this purpose have employed rubber bands or springs so arranged that opening of the mouth tends to draw the lower jaw forward. Another approach has been the use of telescoping but rigid linkages between the upper and lower jaws which push the latter forward when the mouth is closed. Devices which draw the lower jaw forward are taught in U.S. Pat. Nos. 3,618,214 and 3,654,702. Appliances for pushing the lower jaw forward are described by E. Herbst in the magazine "Rundschau", Volume 34, Page 1515, published in 1934, and by M. Northcutt in U.S. Pat. No. 3,798,773 issued in 1971.
A problem with pulling devices has been their inability to produce more than nominal forces on the lower jaw. The force capability of the jaw muscles is much greater when the mouth is being closed than when it is being opened. Another problem with the pulling type of appliance is that the maximum force is exerted when the mouth is wide open. The normal position of the lower jaw during waking hours is such that the mouth is just slightly open. The linkages which induce forward motion of the lower jaw by pulling are therefore less effective than the pushing type.
Pushing appliances as devised by Herbst and Northcutt produce good results but are of relatively large size. Because they are attached to a limited number of teeth in the mandible, prior art pushing devices strongly tend to push the lower anterior teeth (as well as the jaw) forward, an undesirable effect. In addition, they require at least one laboratory fabrication step or possibly more, as the case demands, thus increasing dental chair time in preparation for laboratory models, bite measurements, etc. Another problem with the Herbst and Northcutt appliances, is their difficulty of adjustment once cemented. A further problem involves the linkage which, if too short, may cause the device to become disassembled in the patient's mouth during unexpected "over opening". Furthermore, these appliances inhibit lateral jaw movement. During the months that the patient must wear the appliance, there are continuous occasions when side to side movement must be made. Any limitation of this mobility increases the discomfort of wearing the appliance. It is also important to note that uninterrupted orthodontic treatment of all the teeth does not lend itself to these methods of orthopedic correction because the appliance does not permit the simultaneous use of full continuous arch wires. This shortcoming of the prior art prolongs treatment time because both processes cannot be concurrent.
The present invention overcomes the objection of limited lateral movement by the use of pivoting to achieve mobility in three planes and thus increases patient comfort. The invention also provides a convenient method for adjustment in the patient's mouth without the cutting of metal or the involvement of additional laboratory work. Also, the design of the appliance minimizes the possibility of accidental disassembly while it is in the patient's mouth. It may be used separately as is now done with the Herbst appliance but, more importantly, this invention permits continuous and simultaneous orthodontic treatment during the orthopedic correction and is totally convertible -- i.e., it may be inserted or removed at any time during the orthodontic phase without disturbing installed arch wires.
In another embodiment of the invention, provision is made to assure corrective action during sleep, a hitherto overlooked method for shortening treatment time.
Still another embodiment of the invention permits precision adjustment in the patient's mouth to provide corrective forces exactly suited to the individual.